How can I debug result score

I would like to debug the query result score. I'm doing the query "24" in a meta engine consisting of 2 source engines. I'm getting results back that should be scored equally, but aren't and I can't tell how they would be scored differently. In the screenshot, you can see what these results are. Does anybody have an idea? I tried with the X-Enterprise-Search-Debug header but this does not seem to do anything.

PS: especially the two circled documents should be next to eachother.